The effect of the quantum well structure in green phosphorescent OLED with a mixed host emission interlayer

Abstract

In order to improve the performance of green phosphorescent organic light-emitting diodes, we investigate multiple quantum well (MQW) structure ( ${{\rm CBP/CBP}}_{{{\rm 2/3}}}$ : ${{\rm TPBi}}_{{{\rm 1/3}}}/{{\rm CBP}}$ ) devices with mixed host emission interlayer ( ${{\rm CBP}}_{{{\rm 2/3}}}$ : ${{\rm TPBi}}_{{{\rm 1/3}}}$ ). The four devices with the same thickness of the emission layer (EML) are fabricated, in which the number of quantum well is zero, one, two, and three, respectively. Remarkably, the device with a double MQW structure achieves the maximum luminance, current efficiency and power efficiency values corresponding to ${{\rm 21930\,cd/m}}^{2}$ at 10 V, ${{\rm 48.6\,cd/A}}$ , and ${{\rm 46.4\,lm/W}}$ , respectively. The results also show that the double MQW structure can reduce turn-on voltage from 3.5 to 3 V. We attribute these improvements to the MQW structure which can extend the exciton distribution and avoid space charge accumulation in the EML.